1. Field of the Invention
This invention relates to an abrasive tape for use in the accurate polishing of a magnetic head for a magnetic recording and reproducing apparatus. This invention particularly relates to an abrasive tape for use in polishing of a video magnetic head or a high grade audio magnetic head.
2. Description of the Prior Art
Video or high grade audio magnetic heads are required to have very smooth tape sliding surfaces. Therefore, in general, in the process of making the magnetic head, the tape sliding surface is given a smooth finish by use of an abrasive tape after rough grinding. Particularly, since the video head is required to have a very high smoothness, several types of the abrasive tapes are used for polishing the video tape. Thus the video tape is first polished with a coarse abrasive tape, and finish-polished (scratch polished) with the most smooth abrasive tape at the final stage. The abrasive tape comprises a flexible non-magnetic substrate and fine abrasive particles or the like dispersed and adhered by a binder to the substrate, and can accurately polish the tape sliding surface of the magnetic head by snugly fitting to the curved shape thereof.
As such a tape, there has heretofore been known, a cleaning tape wherein, for example, a vinyl chloride-vinyl acetate copolymer, an epoxy resin and a polyisocyanate are used as the binder.
However, the purpose of the aforesaid tape is mainly to remove dust or the like from the magnetic head. For this purpose, the binder having such an adhesion that the abrasive particles do not separate from the coating film during magnetic head cleaning is used. Therefore, when the tape is used as a tape for polishing the magnetic head, since the adhesion of the binder is too low, the problem that the abrasive particles separate from the coating film during polishing of the magnetic head. Particularly, in the case of the abrasive tape, abrasive particles having large particle sizes are generally used for improving the polishing effects. However, when the average particle size is increased to a value within the range of 5 .mu.m to 30 .mu.m, since the particle size of the largest particle becomes markedly large as compared with the thickness of the coating film and the contact surface area ratio to the binder becomes small, the problem that the abrasive particles more readily separate from the coating film.